1. Field of the Invention
The present invention relates to a novel lighting circuit for a vehicular discharge lamp, which detects the flickering of a discharge lamp due to the expiration of its service life or the like and cuts off the power supply to the discharge lamp, thereby ensuring the safe driving to approaching vehicles.
2. Description of the Related Art
Compact metal halide lamps have recently been receiving greater attention as a light source that can replace an incandescent lamp. A known lighting circuit for a vehicular metal halide lamp uses a DC power source, boosts the DC input voltage by a booster circuit and then converts the boosted voltage into an AC voltage of a sine waveform or rectangular waveform by a DC/AC (Direct Current to Alternate Current) converter before applying the voltage to the metal halide lamp.
When the discharge lamp keeps flickering due to the expiration of the service life during driving, the flickering may dazzle the driver of an approaching vehicle. Driving the vehicle with the flickering discharge lamp is dangerous and may result in serious accidents. The conventional lighting circuit is not however designed to properly cope with such a situation.